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Photic resetting and entrainment in CLOCK-deficient mice
Robert Dallmann1, Jason P DeBruyne, David R Weaver
1Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA. david.weaver@umassmed.edu
Journal of Biological Rhythms
|September 17, 2011
Summary
Mice lacking the CLOCK protein show altered responses to light, particularly large phase advances at night. This abnormal light sensitivity in CLOCK-deficient mice explains their disrupted circadian rhythms.
Area of Science:
- Circadian biology
- Chronobiology
- Molecular biology
Background:
- The CLOCK protein is crucial for regulating circadian rhythms.
- Mice lacking CLOCK protein (Clock(-/-)) exhibit subtle circadian phenotypes.
- Understanding light's impact on these mice is key to deciphering circadian regulation.
Purpose of the Study:
- To comprehensively characterize the circadian phenotype of Clock(-/-) mice under diverse lighting conditions.
- To investigate the phase-response curve (PRC) to light in Clock(-/-) mice.
- To elucidate the mechanisms behind altered light entrainment in CLOCK-deficient mice.
Main Methods:
- Phase-response curve (PRC) experiments using 4-hour light pulses in free-running mice.
- Entrainment studies using skeleton lighting cycles (1L:23D and 1L:10D:1L:12D).
- Assessment of circadian period under constant light conditions.
Main Results:
- Clock(-/-) mice displayed significantly larger phase advances to late-night light pulses compared to controls.
- Morning light exposure induced phase advances in Clock(-/-) mice under skeleton photoperiods, unlike controls.
- CLOCK-deficient mice did not exhibit the typical period-lengthening response to constant light.
Conclusions:
- The abnormal shape of the phase-response curve to light in Clock(-/-) mice underlies their altered circadian phenotypes.
- Disrupted entrainment patterns in CLOCK-deficient mice are linked to their exaggerated responses to specific light phases.
- These findings highlight the critical role of CLOCK protein in modulating light's influence on circadian timing.
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